1. Technical Field
This invention relates to satellite communications, and more particularly to a satellite communication system with improved network architecture for the land-mobile satellite service.
2. Background Information
"Satellite communications" refers to communications via an orbiting communications satellite. The satellite carries communications equipment that relays signals to and from ground stations while the satellite orbits high above earthbound relay stations. Broad coverage results and that attracts the land-mobile service where users may roam over a service area as large as the continental United States.
But existing satellite communications systems have certain drawbacks. Consider, for example, a system having a communications satellite in geosynchronous orbit and a computerized Network Management Center (NMC) on earth. The satellite relays communications from ground stations to the NMC and from the NMC back to the ground stations. In that way, the system channels all ground station communications through the NMC (including both channel requests and traffic) so that the NMC can effectively orchestrate system use according to a predefined protocol.
A ground station wishing to use the system sends a connection request via the satellite to the NMC. Then the NMC makes connection arrangements with that ground station and the ground station being called by communicating with them via the satellite. The two ground stations then connect via the satellite and the NMC over a channel the NMC assigns, and thereafter exchange any of various forms of traffic (e.g., packetized data and voice communications). They continue to exchange traffic that way as long as desired and then relinquish the channel.
But channel availability can be very limited. With 7 MHz uplink and downlink bandwidths, for example, the entire service area has access to relatively few channels compared to a potentially large number of users. That can cause severe traffic congestion. So a need exists for an improved satellite communication system for the land-mobile service that more efficiently accommodates traffic requirements within the available bandwidth--one that maximizes channel availability while minimizing service delays.